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A comment on Proof of work - an unobtrusive alternative to captchas.

Re:Proof of work - an unobtrusive alternative to captchas by yuvadam on Friday May 06, 2011 @05:18AM (#2520444)
Proof of work surely is a very interesting concept, but I'm not sure it's preferable to other methods.

As far as I'm concerned using up 8 seconds of user computation time (during which you cannot guarantee responsiveness) is just as bad as throwing a cryptic CAPTCHA field in her face.

Methods such as timestamping, honeypots and dynamically added fields yield very good results for bot recognition.

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Re:Proof of work - an unobtrusive alternative to captchas by VMG on Friday May 06, 2011 @05:22AM (#2520450)
Can you expand on the timestamping method? I thought this could be easily circumvented by adding random delays to the bot requests.
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Re:Proof of work - an unobtrusive alternative to captchas by bsaunder on Friday May 06, 2011 @06:57AM (#2520613)
See also:

http://news.ycombinator.com/item?id=2368486

(there are lots of comments, a couple of months ago, it would have been easy to see which ones are "interesting", now you must read them all).

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Re:Proof of work - an unobtrusive alternative to captchas by yuvadam on Friday May 06, 2011 @05:24AM (#2520453)
You are absolutely correct. Timestamping alone does not suffice, but it is another layer of defense which does work. Most bots do not have random delays.

I'll try to look up some numbers on this.

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